[1][2] He studied banjo and guitar at Hy Smith's School of Music, developing a distinctive playing style, and began performing in dance bands.

Although he wrote songs and attempted to sell them, he had little success until starting work at a music publishing firm, and forming a songwriting partnership in the mid-1930s with New York-born composer Sol Marcus (1912–1976).

With Marcus, Eddie Durham and Eddie Seiler (1911–1952), he wrote "I Don’t Want to Set the World on Fire", which was first recorded in 1941 by Harlan Leonard and his Kansas City Rockers, and then more successfully by The Ink Spots, whose version reached number 4 on the pop chart, and Horace Heidt, whose recording rose to number 1.

Benjamin, Marcus and Seiler then wrote a second number 1 hit, "When the Lights Go On Again (All Over the World)", recorded by Vaughn Monroe and associated in Britain with Vera Lynn.

After returning to civilian life, he joined with lyricist George David Weiss, and established a second successful songwriting partnership with him.

In 1952, Benjamin and Weiss wrote one of their most successful songs, "Wheel of Fortune", a number 1 hit for Kay Starr which sold over one million copies and provided the theme for a TV show.

He was actively involved in ASCAP, winning an award for "I'll Never Be Free" in 1979, and was on the Council of the American Guild of Authors and Composers.